It is of great urgency and importance to our country both from consideration of our prestige as a nation as well as military necessity that this challenge [Sputnik] be met by an energetic program of research and development for the conquest of space ... It is accordingly proposed that the scientific research be the responsibility of a national civilian agency ... NACA is capable, by rapid extension and expansion of its effort, of providing leadership in
space technology.[16]

While this new federal agency would conduct all non-military space activity, the
Advanced Research Projects Agency (ARPA) was created in February 1958 to develop space technology for military application.[17]

Leadership

The agency's leader,
NASA's administrator, is nominated by the
President of the United States subject to approval of the
US Senate, and reports to him or her and serves as senior space science advisor. Though space exploration is ostensibly non-partisan, the appointee usually is associated with the President's political party (
Democratic or
Republican), and a new administrator is usually chosen when the Presidency changes parties. The only exceptions to this have been:

Democrat
Thomas O. Paine, acting administrator under Democrat
Lyndon B. Johnson, stayed on while Republican
Richard Nixon tried but failed to get one of his own choices to accept the job. Paine was confirmed by the Senate in March 1969 and served through September 1970.[22]

The first administrator was Dr.
T. Keith Glennan appointed by Republican President
Dwight D. Eisenhower. During his term he brought together the disparate projects in American space development research.[24]

The second administrator,
James E. Webb (1961–1968), appointed by President
John F. Kennedy, was a Democrat who first publicly served under President
Harry S. Truman. In order to implement the
Apollo program to achieve Kennedy's Moon landing goal by the end of the 1960s, Webb directed major management restructuring and facility expansion, establishing the Houston Manned Spacecraft (Johnson) Center and the Florida Launch Operations (Kennedy) Center. Capitalizing on Kennedy's legacy, President
Lyndon Johnson kept continuity with the Apollo program by keeping Webb on when he succeeded Kennedy in November 1963. But Webb resigned in October 1968 before Apollo achieved its goal, and Republican President
Richard M. Nixon replaced Webb with Republican
Thomas O. Paine.

Spaceflight programs

NASA is famous for the first human visits to the Moon,[28] (Apollo 8 image of Earth, 1968)

NASA has conducted many crewed and uncrewed spaceflight programs throughout its history. Uncrewed programs launched the first American artificial
satellites into Earth orbit for scientific and
communications purposes, and sent scientific probes to explore the planets of the solar system, starting with
Venus and
Mars, and including "
grand tours" of the outer planets. Crewed programs sent the first Americans into
low Earth orbit (LEO), won the
Space Race with the
Soviet Union by landing twelve men on the Moon from 1969 to 1972 in the
Apollo program, developed a semi-reusable LEO
Space Shuttle, and developed LEO
space station capability by itself and with the cooperation of several other nations including post-Soviet
Russia. Some missions include both crewed and uncrewed aspects, such as the
Galileo probe, which was deployed by astronauts in Earth orbit before being sent uncrewed to Jupiter.

Crewed programs

The experimental
rocket-powered aircraft programs started by NACA were extended by NASA as support for crewed spaceflight. This was followed by a one-man
space capsule program, and in turn by a two-man capsule program. Reacting to loss of national prestige and
security fears caused by early leads in space exploration by the
Soviet Union, in 1961 President
John F. Kennedy proposed the ambitious goal "of landing a man on the Moon by the end of [the 1960s], and returning him safely to the Earth." This goal was met in 1969 by the
Apollo program, and NASA planned even more ambitious activities leading to a
human mission to Mars. However, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory and a semi-reusable Earth orbital shuttle. In the 1990s, funding was approved for NASA to develop a permanent Earth orbital
space station in cooperation with the international community, which now included the former rival, post-Soviet
Russia. To date, NASA has launched a total of 166 crewed space missions on rockets, and thirteen
X-15 rocket flights above the
USAF definition of spaceflight altitude, 260,000 feet (80 km).[29]

X-15 rocket plane (1959–1968)

The
North American X-15 was an NACA experimental rocket-powered
hypersonic research aircraft, developed in conjunction with the US Air Force and Navy. The design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems.[30]Requests for proposal were issued on December 30, 1954, for the airframe, and February 4, 1955, for the rocket engine. The airframe contract was awarded to
North American Aviation in November 1955, and the XLR30 engine contract was awarded to
Reaction Motors in 1956, and three planes were built. The X-15 was
drop-launched from the wing of one of two NASA
Boeing B-52 Stratofortresses, NB52A tail number 52-003, and NB52B, tail number 52-008 (known as the Balls 8). Release took place at an altitude of about 45,000 feet (14 km) and a speed of about 500 miles per hour (805 km/h).

Twelve pilots were selected for the program from the Air Force, Navy, and NACA (later NASA). A total of 199 flights were made between 1959 and 1968, resulting in the
official world record for the highest speed ever reached by a crewed powered aircraft (current as of 2014[update]), and a maximum speed of Mach 6.72, 4,519 miles per hour (7,273 km/h).[31] The altitude record for X-15 was 354,200 feet (107.96 km).[32] Eight of the pilots were awarded Air Force
astronaut wings for flying above 260,000 feet (80 km), and two flights by
Joseph A. Walker exceeded 100 kilometers (330,000 ft), qualifying as spaceflight according to the
International Aeronautical Federation. The X-15 program employed mechanical techniques used in the later crewed spaceflight programs, including
reaction control system jets for controlling the orientation of a spacecraft,
space suits, and horizon definition for navigation.[32] The
reentry and landing data collected were valuable to NASA for designing the
Space Shuttle.[30]

Project Mercury (1958–1963)

Shortly after the Space Race began, an early objective was to get a person into Earth orbit as soon as possible, therefore the simplest spacecraft that could be launched by existing rockets was favored. The US Air Force's
Man in Space Soonest program considered many crewed spacecraft designs, ranging from rocket planes like the X-15, to small ballistic
space capsules.[33] By 1958, the space plane concepts were eliminated in favor of the ballistic capsule.[34]

Project Gemini (1961–1966)

Based on studies to grow the Mercury spacecraft capabilities to long-duration flights, developing
space rendezvous techniques, and precision Earth landing, Project Gemini was started as a two-man program in 1962 to overcome the Soviets' lead and to support the Apollo crewed lunar landing program, adding
extravehicular activity (EVA) and
rendezvous and
docking to its objectives. The first crewed Gemini flight,
Gemini 3, was flown by
Gus Grissom and
John Young on March 23, 1965.[42] Nine missions followed in 1965 and 1966, demonstrating an endurance mission of nearly fourteen days, rendezvous, docking, and practical EVA, and gathering medical data on the effects of weightlessness on humans.[43][44]

Under the direction of
Soviet PremierNikita Khrushchev, the USSR competed with Gemini by converting their Vostok spacecraft into a two- or three-man
Voskhod. They succeeded in launching two crewed flights before Gemini's first flight, achieving a three-cosmonaut flight in 1964 and the first EVA in 1965. After this, the program was canceled, and Gemini caught up while spacecraft designer
Sergei Korolev developed the
Soyuz spacecraft, their answer to Apollo.

Apollo program (1961–1972)

The U.S public's perception of the Soviet lead in the Space Race (by putting the first man into space) motivated President
John F. Kennedy[45] to ask the Congress on May 25, 1961, to commit the federal government to a program to land a man on the Moon by the end of the 1960s, which effectively launched the
Apollo program.[46]

Apollo was one of the most expensive American scientific programs ever. It cost more than $20 billion in 1960s dollars[47] or an estimated $223 billion in present-day US dollars.[48] (In comparison, the
Manhattan Project cost roughly $28.4 billion, accounting for inflation.)[48][49] It used the
Saturn rockets as launch vehicles, which were far bigger than the rockets built for previous projects.[50] The spacecraft was also bigger; it had two main parts, the combined
command and service module (CSM) and the
Apollo Lunar Module (LM). The LM was to be left on the Moon and only the command module (CM) containing the three astronauts would eventually return to Earth.[note 2]

The second crewed mission,
Apollo 8, brought astronauts for the first time in a flight around the Moon in December 1968.[51] Shortly before, the Soviets had sent an uncrewed spacecraft around the Moon.[52] On the next two missions docking maneuvers that were needed for the Moon landing were practiced[53][54] and then finally the Moon landing was made on the
Apollo 11 mission in July 1969.[55]

Apollo set major
milestones in human spaceflight. It stands alone in sending crewed missions beyond
low Earth orbit, and landing humans on another
celestial body.[58]Apollo 8 was the first crewed spacecraft to orbit another celestial body, while
Apollo 17 marked the last moonwalk and the last crewed mission beyond
low Earth orbit. The program spurred advances in many areas of technology peripheral to rocketry and crewed spaceflight, including
avionics, telecommunications, and computers. Apollo sparked interest in many fields of engineering and left many physical facilities and machines developed for the program as landmarks. Many objects and artifacts from the program are on display at various locations throughout the world, notably at the
Smithsonian's Air and Space Museums.

Skylab (1965–1979)

Skylab was the United States' first and only independently built
space station.[59] Conceived in 1965 as a workshop to be constructed in space from a spent
Saturn IB upper stage, the 169,950 lb (77,088 kg) station was constructed on Earth and launched on May 14, 1973, atop the first two stages of a
Saturn V, into a 235-nautical-mile (435 km) orbit inclined at 50° to the equator. Damaged during launch by the loss of its thermal protection and one electricity-generating solar panel, it was repaired to functionality by its first crew. It was occupied for a total of 171 days by 3 successive crews in 1973 and 1974.[59] It included a laboratory for studying the effects of
microgravity, and a
solar observatory.[59] NASA planned to have a Space Shuttle dock with it, and elevate Skylab to a higher safe altitude, but the Shuttle was not ready for flight before Skylab's re-entry on July 11, 1979.[60]

To save cost, NASA used one of the Saturn V rockets originally earmarked for a canceled Apollo mission to launch the Skylab. Apollo spacecraft were used for transporting astronauts to and from the station. Three three-man crews stayed aboard the station for periods of 28, 59, and 84 days. Skylab's habitable volume was 11,290 cubic feet (320 m3), which was 30.7 times bigger than that of the
Apollo Command Module.[60]

Apollo–Soyuz Test Project (1972–1975)

On May 24, 1972, US President
Richard M. Nixon and
Soviet Premier
Alexei Kosygin signed an agreement calling for a joint crewed space mission, and declaring intent for all future international crewed spacecraft to be capable of docking with each other.[61] This authorized the Apollo-Soyuz Test Project (ASTP), involving the rendezvous and docking in Earth orbit of a surplus
Apollo Command/Service Module with a
Soyuz spacecraft. The mission took place in July 1975. This was the last US crewed space flight until the first orbital flight of the
Space Shuttle in April 1981.[62]

The mission included both joint and separate scientific experiments and provided useful engineering experience for future joint US–Russian space flights, such as the Shuttle–Mir Program[63] and the International Space Station.

Space Shuttle program (1972–2011)

NASA officials and politicians welcome the arrival of Spacelab in 1982

The
Space Shuttle became the major focus of NASA in the late 1970s and the 1980s. Planned as a frequently launchable and mostly reusable vehicle, four Space Shuttle orbiters were built by 1985. The first to launch,
Columbia, did so on April 12, 1981,[64] the 20th anniversary of the first known human space flight.[65]

Its major components were a
spaceplane orbiter with an external fuel tank and two solid-fuel launch rockets at its side. The external tank, which was bigger than the spacecraft itself, was the only major component that was not reused. The shuttle could orbit in altitudes of 185–643 km (115–400
miles)[66] and carry a maximum payload (to low orbit) of 24,400 kg (54,000 lb).[67] Missions could last from 5 to 17 days and crews could be from 2 to 8 astronauts.[66]

Mae Jemison working in Spacelab. Spacelab was a major NASA collaboration with space agencies in Europe, who constructed the space laboratory and many of its modular additions.

On 20 missions (1983–98) the Space Shuttle carried
Spacelab, designed in cooperation with the
European Space Agency (ESA). Spacelab was not designed for independent orbital flight, but remained in the Shuttle's cargo bay as the astronauts entered and left it through an
airlock.[68] On June 18, 1983
Sally Ride became the first American woman in space, on board the Space Shuttle ChallengerSTS-7 mission.[69] Another famous series of missions were the
launch and later
successful repair of the
Hubble Space Telescope in 1990 and 1993, respectively.[70]

Launch of a Space Shuttle in 2008

In 1995, Russian-American interaction resumed with the
Shuttle–Mir missions (1995–1998). Once more an American vehicle docked with a Russian craft, this time a full-fledged space station. This cooperation has continued with Russia and the United States as two of the biggest partners in the largest space station built: the
International Space Station (ISS). The strength of their cooperation on this project was even more evident when NASA began relying on Russian launch vehicles to service the ISS during the two-year grounding of the shuttle fleet following the 2003
Space Shuttle Columbia disaster.

The Shuttle fleet lost two orbiters and 14 astronauts in two disasters: Challenger in 1986, and Columbia in 2003.[71] While the 1986 loss was mitigated by building the
Space Shuttle Endeavour from replacement parts, NASA did not build another orbiter to replace the
second loss.[71] NASA's Space Shuttle program had 135 missions when the program ended with the successful landing of the Space Shuttle Atlantis at the Kennedy Space Center on July 21, 2011. The program spanned 30 years with over 300 astronauts sent into space.[72]

Long-duration missions to the ISS are referred to as
ISS Expeditions. Expedition crew members typically spend approximately six months on the ISS.[81] The initial expedition crew size was three, temporarily decreased to two following the Columbia disaster. Since May 2009, expedition crew size has been six crew members.[82] Crew size is expected to be increased to seven, the number the ISS was designed for, once the Commercial Crew Program becomes operational.[83] The ISS has been continuously occupied for the past 19 years and 217 days, having exceeded the previous record held by Mir; and has been visited by astronauts and cosmonauts from
15 different nations.[84][85]

The station can be seen from the Earth with the naked eye and, as of 2020, is the largest artificial satellite in
Earth orbit with a mass and volume greater than that of any previous space station.[86] The
Soyuz spacecraft delivers crew members, stays docked for their half-year-long missions and then returns them home. Several uncrewed cargo spacecraft service the ISS; they are the Russian
Progress spacecraft which has done so since 2000, the European
Automated Transfer Vehicle (ATV) since 2008, the Japanese
H-II Transfer Vehicle (HTV) since 2009, the American
Dragon spacecraft since 2012, and the American
Cygnus spacecraft since 2013. The Space Shuttle, before its retirement, was also used for cargo transfer and would often switch out expedition crew members, although it did not have the capability to remain docked for the duration of their stay. Until another US crewed spacecraft is ready, crew members will travel to and from the International Space Station exclusively aboard the Soyuz.[87] The highest number of people occupying the ISS has been thirteen; this occurred three times during the late Shuttle ISS assembly missions.[88]

The ISS program is expected to continue to 2030.[89] On March 29, 2019, the ISS had its first all-female spacewalk;
Anne McClain and
Christina Koch will take flight during Women's History Month.[90]

Commercial programs (2006–present)

The development of the Commercial Resupply Services (CRS) vehicles began in 2006 with the purpose of creating American commercially operated uncrewed cargo vehicles to service the ISS.[91] The development of these vehicles was under a fixed-price, milestone-based program, meaning that each company that received a funded award had a list of milestones with a dollar value attached to them that they did not receive until after they had successfully completed the milestone.[92] Companies were also required to raise an unspecified amount of private investment for their proposal.[93]

The
Commercial Crew Development (CCDev) program was started in 2010 with the purpose of creating American commercially operated crewed spacecraft capable of delivering at least four crew members to the ISS, staying docked for 180 days and then returning them back to Earth.[99] It is hoped that these vehicles could also transport non-NASA customers to private space stations such those planned by
Bigelow Aerospace.[100] Like COTS, CCDev is a fixed-price, milestone-based developmental program that requires some private investment.[92]

In 2010, when NASA announced the winners of the first phase of the program, a total of $50 million was divided among five American companies to foster research and development into human spaceflight concepts and technologies in the private sector. In 2011, the winners of the second phase of the program were announced, and $270 million was divided among four companies.[101] In 2012, the winners of the third phase of the program were announced; NASA provided $1.1 billion divided among three companies to further develop their crew transportation systems.[102] In 2014, the winners of the final round were announced.[103] SpaceX
Crew Dragon (launched on a
Falcon 9 Block 5) received a contract valued up to $2.6 billion and Boeing's
CST-100 (to be launched on an
Atlas V) received a contract valued up to $4.2 billion.[104] NASA expects these vehicles to begin transporting humans to the ISS in 2020, with the launch of
SpaceX Demo-2 on 30 May 2020.

Constellation program (2005–2009) and Journey To Mars (2010–2017)

While the Space Shuttle program was still suspended after the loss of Columbia, President
George W. Bush announced the
Vision for Space Exploration including the retirement of the Space Shuttle after completing the International Space Station. The plan was enacted into law by the
NASA Authorization Act of 2005 and directs NASA to develop and launch the
Crew Exploration Vehicle (later called
Orion) by 2010, return Americans to the Moon by 2020, return to Mars as feasible, repair the
Hubble Space Telescope, and continue scientific investigation through robotic solar system exploration, human presence on the ISS, Earth observation, and astrophysics research. The crewed exploration goals prompted NASA's
Constellation program.

After the
Augustine Committee found that the Constellation program could not meet its goals without substantially more funding, in February 2010, President
Barack Obama's administration proposed eliminating public funds for it.[105] Obama's plan was to develop American
private spaceflight capabilities to get astronauts to the International Space Station, replacing Russian Soyuz capsules, and to use Orion capsules for ISS emergency escape purposes. During a speech at the Kennedy Space Center on April 15, 2010, Obama proposed a new heavy-lift vehicle (HLV) to replace the formerly planned
Ares V.[106] In his speech, Obama called for a crewed mission to an asteroid as soon as 2025, and a crewed mission to Mars orbit by the mid-2030s.[106] The
NASA Authorization Act of 2010 was passed by Congress and signed into law on October 11, 2010.[107] The act officially canceled the Constellation program.[107]

The NASA Authorization Act of 2010 required a newly designed HLV be chosen within 90 days of its passing; the launch vehicle was given the name
Space Launch System. The new law also required the construction of a beyond low earth orbit spacecraft.[108] The
Orion spacecraft, which was being developed as part of the Constellation program, was chosen to fulfill this role.[109] The Space Launch System is planned to launch both Orion and other necessary hardware for missions beyond low Earth orbit.[110] The SLS is to be upgraded over time with more powerful versions. The initial capability of SLS is required to be able to lift 70 t (150,000 lb) (later 95 t or 209,000 lb) into
LEO. It is then planned to be upgraded to 105 t (231,000 lb) and then eventually to 130 t (290,000 lb).[109][111] The Orion capsule first flew on
Exploration Flight Test 1 (EFT-1), an uncrewed test flight that was launched on December 5, 2014, atop a
Delta IV Heavy rocket.[111]

NASA undertook a feasibility study in 2012 and developed the
Asteroid Redirect Mission as an uncrewed mission to move a boulder-sized
near-Earth asteroid (or boulder-sized chunk of a larger asteroid) into lunar orbit. The mission would demonstrate
ion thruster technology, and develop techniques that could be used for
planetary defense against an asteroid collision, as well as cargo transport to Mars in support of a future human mission. The Moon-orbiting boulder might then later be visited by astronauts. The Asteroid Redirect Mission was cancelled in 2017 as part of the FY2018 NASA budget, the first one under President
Donald Trump.

Artemis program (2017–present)

Since 2017, NASA's
crewed spaceflight program has been the
Artemis program, which involves the help of U.S.
commercial spaceflight companies and international partners such as
ESA.[112] The goal of this program is to land "the first woman and the next man" on the
lunar south pole region by 2024. Artemis would be the first step towards the long-term goal of establishing a sustainable presence on the Moon, laying the foundation for private companies to build a lunar economy, and eventually sending humans to
Mars.

The Orion Crew Exploration Vehicle was held over from the canceled Constellation program for Artemis.
Artemis 1 is the uncrewed initial launch of SLS that would also send an Orion spacecraft on a
Distant Retrograde Orbit, which is planned to launch no earlier than November 2020.[113]

Concepts for how the first human landing site on Mars might evolve over the course of multiple human expeditions

NASA's next major space initiative is to be the construction of the
Lunar Gateway. This initiative is to involve the construction of a new space station, which will have many features in common with the current
International Space Station, except that it will be in orbit about the Moon, instead of the Earth.[114] This space station will be designed primarily for non-continuous human habitation. The first tentative steps of returning to crewed lunar missions will be
Artemis 2, which is to include the Orion crew module, propelled by the SLS, and is to launch in 2022.[112] This mission is to be a 10-day mission planned to briefly place a crew of four into a
Lunar flyby.[111] The construction of the Gateway would begin with the proposed Artemis 3, which is planned to deliver a crew of four to
Lunar orbit along with the first modules of the Gateway. This mission would last for up to 30 days. NASA plans to build full scale deep space habitats such as the Lunar Gateway and the
Nautilus-X as part of its
Next Space Technologies for Exploration Partnerships (NextSTEP) program.[115] In 2017, NASA was directed by the congressional NASA Transition Authorization Act of 2017 to get humans to Mars-orbit (or to the Martian surface) by 2030s.[116][117]

On June 5, 2016, NASA and DARPA announced plans to also build a series of new X-planes over the next 10 years.[118] One of the planes will be the
Quiet Supersonic Technology project, burning low-carbon
biofuels and generating quiet sonic booms.[118]

Uncrewed programs

More than 1,000 uncrewed missions have been designed to explore the Earth and the solar system.[119] Besides exploration, communication satellites have also been launched by NASA.[120] The missions have been launched directly from Earth or from orbiting space shuttles, which could either deploy the satellite itself, or with a rocket stage to take it farther.

The first US uncrewed satellite was
Explorer 1, which started as an ABMA/JPL project during the early part of the
Space Race. It was launched in January 1958, two months after Sputnik. At the creation of NASA, the Explorer project was transferred to the agency and still continues to this day. Its missions have been focusing on the Earth and the Sun, measuring magnetic fields and the
solar wind, among other aspects.[121] A more recent Earth mission, not related to the Explorer program, was the
Hubble Space Telescope, which was brought into orbit in 1990.[122]

The
inner Solar System has been made the goal of at least four uncrewed programs. The first was
Mariner in the 1960s and 1970s, which made multiple visits to
Venus and
Mars and one to
Mercury. Probes launched under the Mariner program were also the first to make a planetary flyby (
Mariner 2), to take the first pictures from another planet (
Mariner 4), the first planetary orbiter (
Mariner 9), and the first to make a
gravity assist maneuver (Mariner 10). This is a technique where the satellite takes advantage of the gravity and velocity of planets to reach its destination.[123]

Video of many of the uncrewed missions were used to explore the outer reaches of space

Outside Mars, Jupiter was first visited by Pioneer 10 in 1973. More than 20 years later Galileo sent a probe into the planet's atmosphere, and became the first spacecraft to orbit the planet.[125]Pioneer 11 became the first spacecraft to visit
Saturn in 1979, with Voyager 2 making the first (and so far only) visits to
Uranus and
Neptune in 1986 and 1989, respectively. The first spacecraft to leave the solar system was Pioneer 10 in 1983. For a time it was the most distant spacecraft, but it has since been surpassed by both Voyager 1 and Voyager 2.[126]

Pioneers 10 and 11 and both Voyager probes carry messages from the Earth to extraterrestrial life.[127][128] Communication can be difficult with deep space travel. For instance, it took about three hours for a radio signal to reach the New Horizons spacecraft when it was more than halfway to Pluto.[129] Contact with Pioneer 10 was lost in 2003. Both Voyager probes continue to operate as they explore the outer boundary between the Solar System and interstellar space.[130]

On November 26, 2011, NASA's
Mars Science Laboratory mission was successfully launched for Mars. Curiosity successfully landed on Mars on August 6, 2012, and subsequently began its search for evidence of past or present life on Mars.[131][132][133]

Activities (2005–2017)

The EFT-1 test flight was conducted in 2014, uncrewed capsule shown

NASA's ongoing investigations include in-depth surveys of Mars (
Perseverance and
InSight) and Saturn and studies of the Earth and the Sun. Other active spacecraft missions are Juno for
Jupiter, New Horizons (for Jupiter,
Pluto, and beyond), and Dawn for the
asteroid belt. NASA continued to support in situ exploration beyond the asteroid belt, including Pioneer and Voyager traverses into the unexplored trans-Pluto region, and
Gas Giant orbiters Galileo (1989–2003), Cassini (1997–2017), and Juno (2011–). In the early 2000s, NASA was put on course for the Moon, however, in 2010 this program was cancelled (see
Constellation program). As part of that plan, the Shuttle was going to be replaced, however, although it was retired its replacement was also cancelled, leaving the US with no human spaceflight launcher for the first time in over three decades.

On December 4, 2006, NASA announced it was planning a
permanent Moon base.[135] The goal was to start building the Moon base by 2020, and by 2024, have a fully functional base that would allow for crew rotations and
in-situ resource utilization. However, in 2009, the
Augustine Committee found the program to be on an "unsustainable trajectory."[136] In 2010, President
Barack Obama halted existing plans, including the Moon base, and directed a generic focus on crewed missions to asteroids and Mars, as well as extending support for the International Space Station.[137]

In September 2011, NASA announced the start of the
Space Launch System program to develop a human-rated heavy lift vehicle. The Space Launch System is intended to launch the
Orion spacecraft and other elements towards the
Moon and
Mars.[140] The Orion spacecraft conducted an uncrewed test launch on a
Delta IV Heavy rocket in December 2014.[141]

On August 6, 2012, NASA landed the rover Curiosity on Mars. On August 27, 2012, Curiosity transmitted the first pre-recorded message from the surface of Mars back to Earth, made by Administrator Charlie Bolden:

Hello. This is Charlie Bolden, NASA Administrator, speaking to you via the broadcast capabilities of the Curiosity rover, which is now on the surface of Mars.

Since the beginning of time, humankind's curiosity has led us to constantly seek new life ... new possibilities just beyond the horizon. I want to congratulate the men and women of our NASA family as well as our commercial and government partners around the world, for taking us a step beyond to Mars.

This is an extraordinary achievement. Landing a rover on Mars is not easy – others have tried – only America has fully succeeded. The investment we are making ... the knowledge we hope to gain from our observation and analysis of Gale Crater, will tell us much about the possibility of life on Mars as well as the past and future possibilities for our own planet. Curiosity will bring benefits to Earth and inspire a new generation of scientists and explorers, as it prepares the way for a human mission in the not too distant future. Thank you.[142]

In 1994, there was a Congressional directive to find near-Earth objects (NEOs) larger than 1 kilometer, and 90% of 1 kilometer sized asteroids are estimated to have been found by 2010.[144]

Plot of orbits of known Potentially Hazardous Asteroids (size over 460 feet (140 m) and passing within 4.7 million miles (7.6×10^6 km) of Earth's orbit)

NASA visited a near-Earth asteroid with a probe for the first time in 1998(flyby)/2000(orbit), asteroid 433 Eros

In 2005, the US Congress mandated NASA to achieve by the year 2020 specific levels of search completeness for discovering, cataloging, and characterizing dangerous asteroids larger than 140 meters (460 ft) (Act of 2005, H.R. 1022; 109th),[145][146] but no new funds were appropriated for this effort.[147] As of January 2019, it is estimated about 40% of the NEOs of this size have been found, although since by its nature the exact amount of NEOs are unknown the calculations are based on predictions of how many there could be.[148]

(d) Near-Earth Object Survey.--
(1) Survey program.--The Administrator shall plan, develop,
and implement a Near-Earth Object Survey program to detect,
track, catalogue, and characterize the physical characteristics
of near-Earth objects equal to or greater than 140 meters in
diameter in order to assess the threat of such near-Earth
objects to the Earth. <<NOTE: Deadline.>> It shall be the goal
of the

Page 119 STAT. 2923

Survey program to achieve 90 percent completion of its near-
Earth object catalogue (based on statistically predicted
populations of near-Earth objects) within 15 years after the

NEOs were defined in this case by the term near-Earth object as an asteroid or comet with a perihelion distance of less
than 1.3 Astronomical Units from the Sun.[150] In late 2019 the directive gained increased notoriety and NASA approved an additional space telescope in addition to the existing observatory programs.[151]

One issue with NEO prediction is trying to estimate how many more are likely to be found In 2000, NASA reduced its estimate of the number of existing near-Earth asteroids over one kilometer in diameter from 1,000–2,000 to 500–1,000.[152][153] Shortly thereafter, the
LINEAR survey provided an alternative estimate of 1,227+170−90.[154] In 2011, on the basis of NEOWISE observations, the estimated number of one-kilometer NEAs was narrowed to 981±19 (of which 93% had been discovered at the time), while the number of NEAs larger than 140 meters across was estimated at 13,200±1,900.[155][156] The NEOWISE estimate differed from other estimates in assuming a slightly lower average asteroid albedo, which produces larger estimated diameters for the same asteroid brightness. This resulted in 911 then known asteroids at least 1 km across, as opposed to the 830 then listed by CNEOS.[157] In 2017, using an improved statistical method, two studies reduced the estimated number of NEAs brighter than absolute magnitude 17.75 (approximately over one kilometer in diameter) to 921±20.[158][159] The estimated number of asteroids brighter than absolute magnitude of 22.0 (approximately over 140 m across) rose to 27,100±2,200, double the WISE estimate,[159] of which about a third are known as of 2018. A problem with estimating the number of NEOs is that detections are influenced by a number of factors.[160]Observational biases need to be taken into account when trying to calculate the number of bodies in a population.[160] What is easily detected will be more counted.[161]

Large Earth NEO collisions are seen as unlikely but possible.

For example, it has been easier to spot objects on the night-side of Earth. There is less noise from twilight, and the searcher is looking at the sunlit side of the asteroids. In the daytime sky, a searcher looking towards the sun sees the backside of the object (e.g. comparing a
Full Moon at night to a
New Moon in daytime). In addition,
opposition surge make them even brighter when the Earth is along the axis of sunlight. Finally, the day sky near the Sun is bright.[161] The light of sun hitting asteroids has been called "full asteroid" similar to a "full Moon" and the greater amount of light, creates a bias that makes them easier to detect in this case.[161]

Over half (53%) of the discoveries of Near Earth objects were made in 3.8% of the sky, in a 22.5°
cone facing directly away from the Sun, and the vast majority (87%) were made in 15% of the sky, in a 45°
cone facing away from the Sun.[162]

WISE infrared telescope

NASA turned the infrared space survey telescope WISE back on in 2013 to look for NEOs, and it found some during the course of its operation. NEOcam competed in the highly competitive Discovery program, which became more so due to a low mission rate in the 2010s. Also the Mars Scout Program was terminated at that time, further increasing competition. From its start until 2010, ten missions where launched, only two more mission were launched by 2020 (to the Moon and Mars), additionally the Mars Scout program had launched two additional programs to the planet Mars, which competed with NEOcam as well as more obscure destinations like Venus, which has had no dedicated mission since the 1980s. Finally, NASA plans to turn off its existing Infrared Great Observatory, the Spitzer Space Telescope in 2021 due to technical problems (It is drifting away from the Earth in an Earth-trailing orbit which means it must rotate at extreme angle to communicate with Earth, but keep its battery charge).

Background

Two of the biggest Near-Earth objects,
433 Eros and
1036 Ganymed, were among the first Near Earth asteroids to be detected.[163] As bigger asteroids they reflected more light.[161] The eccentric 433 asteroid was discovered by German astronomer
Carl Gustav Witt at the
Berlin Urania Observatory on August 13, 1898.[164] 1036 Ganymed is about 20 miles (35 km) in diameter,[163] and it was discovered by German astronomer
Walter Baade at the
Bergedorf Observatory in Hamburg on October 23, 1924.[165][166] In 1999 NASA visited 433 Eros with the NEAR spacecraft which entered its orbit in 2000, closely imaging the asteroid with various instruments at that time.[167] From the 1990s NASA has run many NEO detection programs from Earth bases observatories, greatly increasing the number of objects that have been detected. However, many asteroids are very dark and the ones that are near the Sun are much harder to detect from Earth-based telescopes which observe at night, and thus face away from the Sun. NEOs inside Earth orbit only reflect a part of light also rather than potentially a "full Moon" when they are behind the Earth and fully lit by the Sun.

Due to the opposition effect over half (53%) of the discoveries of
Near Earth objects were made in 3.8% of the sky, in a 22.5°
cone facing directly away from the Sun, and the vast majority (87%) were made in 15% of the sky, in a 45°
cone facing away from the Sun.[162]

Recent and planned activities

Animation of a robotic arm moving on the
OSIRIS-REx mission to retrieve a sample from an asteroid

Published by NASA in March 2019, the "Jupiter Marble" by the Juno probe, in orbit around planet Jupiter

The Kuiper belt object
486958 Arrokoth was imaged during a flyby on January 1, 2019 by the New Horizons probe.[168]

NASA's ongoing investigations include in-depth surveys of Mars (
Mars 2020 and InSight) and Saturn and studies of the Earth and the Sun. Other active spacecraft missions are Juno for
Jupiter, New Horizons (for Jupiter,
Pluto, and beyond), and Dawn for the
asteroid belt. NASA continued to support in situ exploration beyond the asteroid belt, including Pioneer and Voyager traverses into the unexplored trans-Pluto region, and
Gas Giant orbiters Galileo (1989–2003), Cassini (1997–2017), and Juno (2011–).

In 2017, President
Donald Trump directed NASA to send Humans to Mars by the year 2033.[116][169] Foci in general for NASA were noted as human space exploration, space science, and technology.[169] The Europa Clipper and
Mars 2020 continue to be supported for their planned schedules.[170]

In 2018, NASA along with other companies including
Sensor Coating Systems,
Pratt & Whitney, Monitor Coating and
UTRC launched the project CAUTION (CoAtings for Ultra High Temperature detectION). This project aims to enhance the temperature range of the
Thermal History Coating up to 1,500C and beyond. The final goal of this project is improving the safety of jet engines as well as increasing efficiency and reducing CO2 emissions.[171]

The Northrop Grumman Antares rocket, with Cygnus resupply spacecraft on board, launches from Pad-0A, Wednesday, April 17, 2019 at NASA's Wallops Flight Facility in Virginia. Northrop Grumman's 11th contracted cargo resupply mission for NASA to the International Space Station will deliver about 7,600 pounds of science and research, crew supplies and vehicle hardware to the orbital laboratory and its crew.[172]

NASA Advisory Council

In response to the
Apollo 1 accident, which killed three astronauts in 1967, Congress directed NASA to form an Aerospace Safety Advisory Panel (ASAP) to advise the NASA Administrator on safety issues and hazards in NASA's aerospace programs. In the aftermath of the
Shuttle Columbia disaster, Congress required that the ASAP submit an annual report to the NASA Administrator and to Congress.[177] By 1971, NASA had also established the Space Program Advisory Council and the Research and Technology Advisory Council to provide the administrator with advisory committee support. In 1977, the latter two were combined to form the NASA Advisory Council (NAC).[178]

Directives

Artistic rendition of Space Station Freedom with the Space Shuttle Orbiter Vehicle

Some of NASA's main directives have been the landing of a manned spacecraft on the Moon, the designing and construction of the Space Shuttle, and efforts to construct a large, crewed space station. Typically, the major directives originated from the intersection of scienctific interest and advice, political interests, federal funding concerns, and the public interest, that all together brought varying waves of effort, often heavily swayed by technical developments, funding changes, and world events. For example, in the 1980s, the Reagan administration announced a directive with a major push to build a crewed space station, given the name
Space Station Freedom.[179] But, when the Cold War ended, Russia, the United States, and other international partners came together to design and build the
International Space Station.

In the 2010s, major shifts in directives include retirement of the
Space Shuttle, and the later development of a new crewed heavy lift rocket, the
Space Launch System. Missions for the new
Space Launch System have varied, but overall, NASA's directives are similar to the
Space Shuttle program as the primary goal and desire is human spaceflight. Additionally, NASA's
Space Exploration Initiative of the 1980s opened new avenues of exploration focused on other galaxies.

For the coming decades, NASA's focus has gradually shifting towards eventual exploration of Mars.[180] One of the technological options focused on was the
Asteroid Redirect Mission (ARM).[180] ARM had largely been defunded in 2017, but the key technologies developed for ARM would be utilized for future exploration, notably on a solar electric propulsion system.[181][180]

Longer project execution timelines leaves future executive administration officials to execute on a directive, which can lead to directional mismanagement.

Previously, in the early 2000s, NASA worked towards a strategic plan called the
Constellation Program, but the program was defunded in the early 2010s.[182][183][184][185] In the 1990s, the NASA administration adopted an approach to planning coined "Faster, Better, Cheaper".[186]

NASA Authorization Act of 2017

Orion at ISS artwork

The NASA Authorization Act of 2017, which included $19.5 billion in funding for that fiscal year, directed NASA to get humans near or on the surface of Mars by the early 2030s.[187]

Though the agency is independent, the survival or discontinuation of projects can depend directly on the will of the President.[188]

Space Policy Directive 1

In December 2017, on the 45th anniversary of the last crewed mission to the Lunar surface, President
Donald Trump approved a directive that includes a lunar mission on the pathway to Mars and beyond.[180]

We'll learn. The directive I'm signing today will refocus America's space program on human exploration and discovery. It marks an important step in returning American astronauts to the Moon for the first time since 1972 for long-term exploration and use. This time, we will not only plant our flag and leave our footprint, we will establish a foundation for an eventual mission to Mars. And perhaps, someday, to many worlds beyond.

New NASA administrator
Jim Bridenstine addressed this directive in an August 2018 speech where he focused on the sustainability aspects—going to the Moon to stay—that are explicit in the directive, including taking advantage of US commercial space
capability that did not exist even five years ago, which have
driven down costs and increased access to space.[190]

NASA started an annual competition in 2014 named Cubes in Space.[195] It is jointly organized by NASA and the global education company I Doodle Learning, with the objective of teaching school students aged 11–18 to design and build scientific experiments to be launched into space on a NASA rocket or balloon. On June 21, 2017 the world's smallest satellite,
Kalam SAT, built by an Indian team, was launched.[196]

NASA contracted a third party to study the probability of using Free Space Optics (FSO) to communicate with Optical (
laser) Stations on the Ground (OGS) called laser-com
RF networks for satellite communications.[201]

Use of the International System of Units

US law requires the
International System of Units to be used in all U.S. Government programs, "except where impractical".[202] Today NASA is predominantly working with SI units, but some projects still use a mix of US and SI units.

Facilities

NASA Headquarters in Washington, DC provides overall guidance and political leadership to the agency's ten field centers, through which all other facilities are administered. The ten field centers are:

A
Ball Aerospace engineer performs final checks before the spacecraft shipped to NASA's Kennedy Space Center in Florida for launch processing.

John F. Kennedy Space Center (KSC) is one of the best-known NASA facilities. It has been the launch site for every U.S. human space flight since 1968. KSC manages and operates rocket launch facilities for America's civilian space program from three pads at the adjoining Cape Canaveral Air Force Station. NASA also operates a
short-line railroad at KSC and uses special aircraft.

Langley Research Center (LaRC), founded in 1917, is the oldest of NASA's field centers, located in
Hampton, Virginia. LaRC focuses primarily on aeronautical research, though the
Apollo lunar lander was flight-tested at the facility and a number of high-profile space missions have been planned and designed on-site. Langley currently devotes two-thirds of its programs to
aeronautics, and the rest to
space.

NASA's share of the total federal budget peaked at approximately 4.41% in 1966 during the
Apollo program, then rapidly declined to approximately 1% in 1975, and stayed around that level through 1998.[188][207] The percentage then gradually dropped, until leveling off again at around half a percent in 2006 (estimated in 2012 at 0.48% of the federal budget).[208] In a March 2012 hearing of the
United States Senate Science Committee,
science communicatorNeil deGrasse Tyson testified that "Right now, NASA's annual budget is half a penny on your tax dollar. For twice that—a penny on a dollar—we can transform the country from a sullen, dispirited nation, weary of economic struggle, to one where it has reclaimed its 20th century birthright to dream of tomorrow."[209][210]

Despite this, public perception of NASA's budget differs significantly: a 1997 poll indicated that most Americans believed that 20% of the federal budget went to NASA.[211]

For Fiscal Year 2015, NASA received an appropriation of US$18.01 billion from Congress—$549 million more than requested and approximately $350 million more than the 2014 NASA budget passed by Congress.[212]

President
Donald Trump signed the NASA Transition Authorization Act of 2017 in March, which set the 2017 budget at around $19.5 billion.[169] The budget is also reported as $19.3 billion for 2017, with $20.7 billion proposed for FY2018.[213][214]

Environmental impact

NASA vision for the first Humans On Mars(Artist Concept; June 12, 2019)

By expanding to a new planet, additional knowledge about environment can be acquired, such as eating insects for food.[215]

The exhaust gases produced by rocket propulsion systems, both in Earth's atmosphere and in space, can adversely effect the Earth's environment. Some
hypergolic rocket propellants, such as
hydrazine, are highly toxic prior to
combustion, but decompose into less toxic compounds after burning. Rockets using hydrocarbon fuels, such as
kerosene, release carbon dioxide and soot in their exhaust.[216] However, carbon dioxide emissions are insignificant compared to those from other sources; on average, the United States consumed 802,620,000 US gallons (3.0382×109 L) of liquid fuels per day in 2014, while a single
Falcon 9 rocket first stage burns around 25,000 US gallons (95,000 L) of
kerosene fuel per launch.[217][218] Even if a Falcon 9 were launched every single day, it would only represent 0.006% of liquid fuel consumption (and carbon dioxide emissions) for that day. Additionally, the exhaust from
LOx- and
LH2- fueled engines, like the
SSME, is almost entirely water vapor.[219] NASA addressed environmental concerns with its canceled
Constellation program in accordance with the National Environmental Policy Act in 2011.[220] In contrast,
ion engines use harmless noble gases like
xenon for propulsion.[221][222]

Here are some selected examples of missions to planetary-sized objects. Other major targets of study are the Earth itself, the Sun, and smaller Solar System bodies like asteroids and comets. In addition, the moons of the planets or body are also studied.

^Foust, Jeff (September 19, 2014).
"NASA Commercial Crew Awards Leave Unanswered Questions". Space News. Retrieved September 21, 2014. We basically awarded based on the proposals that we were given," Kathy Lueders, NASA commercial crew program manager, said in a teleconference with reporters after the announcement. "Both contracts have the same requirements. The companies proposed the value within which they were able to do the work, and the government accepted that.

^"Short-Term Energy Outlook"(PDF). U.S. Energy Information Administration. February 9, 2016.
Archived(PDF) from the original on March 18, 2016. Retrieved February 24, 2016. U.S. Petroleum and Other Liquids